differentiate type=text and type=taxonomy when using the same id

given:
- post_meta field 'city'
- taxonomy with query_var 'city'

code:

[
    'type' => 'text',
    'name' => 'City',
    'id'   => 'city',
    'std'  => '',
]

problem:
The meta box text field is being filled with the taxonomy term 'city' instead of the post_meta value 'city'.
When I save the post, the updated value entered into the text field is neither being written to the post_meta 'city', nor a taxonomy term is being created/assigned.

desired behavior:
- read and save fields using 'type' => 'text' from post_meta 'city', only
- read and save fields using 'type' => 'taxonomy' from taxonomy 'city', only